全文获取类型
收费全文 | 1013篇 |
免费 | 103篇 |
国内免费 | 92篇 |
专业分类
化学 | 582篇 |
力学 | 75篇 |
综合类 | 5篇 |
数学 | 103篇 |
物理学 | 443篇 |
出版年
2024年 | 4篇 |
2023年 | 103篇 |
2022年 | 19篇 |
2021年 | 12篇 |
2020年 | 22篇 |
2019年 | 24篇 |
2018年 | 26篇 |
2017年 | 28篇 |
2016年 | 15篇 |
2015年 | 19篇 |
2014年 | 50篇 |
2013年 | 56篇 |
2012年 | 44篇 |
2011年 | 53篇 |
2010年 | 59篇 |
2009年 | 62篇 |
2008年 | 67篇 |
2007年 | 69篇 |
2006年 | 51篇 |
2005年 | 72篇 |
2004年 | 70篇 |
2003年 | 48篇 |
2002年 | 32篇 |
2001年 | 25篇 |
2000年 | 25篇 |
1999年 | 12篇 |
1998年 | 33篇 |
1997年 | 16篇 |
1996年 | 9篇 |
1995年 | 14篇 |
1994年 | 14篇 |
1993年 | 10篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有1208条查询结果,搜索用时 171 毫秒
71.
72.
近年来,2,2′:6′,2″-联三吡啶作为典型的三齿有机杂环配体在超分子化学与材料化学领域得到广泛应用。通过取代基团对配体的结构修饰或改变金属离子的类型可以调控联三吡啶金属络合物的光物理和电化学性能,从而得到多种不同用途的功能化材料及超分子组装体。本文对单核联三吡啶配体近年来发展的典型合成方法加以阐述,并简单介绍联三吡啶配体在超分子化学中的应用。 相似文献
73.
74.
The Pure Adaptive Search (PAS) algorithm for global optimization yields a sequence of points, each of which is uniformly distributed in the level set corresponding to its predecessor. This algorithm has the highly desirable property of solving a large class of global optimization problems using a number of iterations that increases at most linearly in the dimension of the problem. Unfortunately, PAS has remained of mostly theoretical interest due to the difficulty of generating, in each iteration, a point uniformly distributed in the improving feasible region. In this article, we derive a coupling equivalence between generating an approximately uniformly distributed point using Markov chain sampling, and generating an exactly uniformly distributed point with a certain probability. This result is used to characterize the complexity of a PAS-implementation as a function of (a) the number of iterations required by PAS to achieve a certain solution quality guarantee, and (b) the complexity of the sampling algorithm used. As an application, we use this equivalence to show that PAS, using the so-called Random ball walk Markov chain sampling method for generating nearly uniform points in a convex region, can be used to solve most convex programming problems in polynomial time. 相似文献
75.
I.M. KrishnakumarBeena Mathew 《European Polymer Journal》2002,38(9):1745-1752
To correlate the coupling difficulty and nature of the support in solid-phase peptide synthesis, a set of difficult peptides were built under identical conditions on rigid and hydrophobic divinyl benzene-crosslinked polystyrene (DVB-PS) and flexible and polar 1,4-butanediol dimethacrylate-crosslinked polystyrene (BDDMA-PS) resins of same functional capacity (∼2 mmol/g). The difficult coupling stages observed on each support were identified by monitoring the acylation time, coupling yield and deprotection efficiency. The yield and purity of the peptides prepared on BDDMA-PS were higher than when DVB-PS support was used. 相似文献
76.
77.
Yevgeniy Kovchegov 《Journal of Theoretical Probability》2008,21(2):437-448
We consider a multi-particle generalization of linear edge-reinforced random walk (ERRW). We observe that in absence of exchangeability,
new techniques are needed in order to study the multi-particle model. We describe an unusual coupling construction associated
with the two-point edge-reinforced process on ℤ and prove a form of recurrence: the two particles meet infinitely often a.s.
This research was supported in part by NSF VIGRE Grant DMS 9983726 at UCLA. 相似文献
78.
Fubao Xi 《Journal of Mathematical Analysis and Applications》2008,341(1):588-600
In this paper we consider the stability for a class of jump-diffusions with Markovian switching. We first construct them successively and show that they can be associated with some appropriate generators and they are non-explosive. We then prove their Feller continuity by the coupling methods. Furthermore, we also prove their strong Feller continuity by making use of the relation between the transition probabilities of jump-diffusions and the corresponding diffusions. Finally, we also investigate their exponential ergodicity. 相似文献
79.
A novel efficient synthetic method for 2,2',3,3'-biphenyltetracarboxylic dianhydride 总被引:1,自引:0,他引:1
A novel approach to the synthesis of 2,2',3,3'-biphenyltetracarboxylic dianhydride is described. The target compound was prepared by a nickel-catalyzed coupling reaction of dimethy 3-chlorophthalate (3-DMCP) for 4 h at 70-80℃, followed by subsequent hydrolysis of tetra-ester in acid solution and dehydration of tetra-acid, with overall yield of 68%. The structures of the products were characterized by IR, 1H NMR and 13C NMR respectively. 相似文献
80.
Jean-Paul Penot 《Journal of Global Optimization》2008,40(1-3):319-338
We look for a general framework in which the Ekeland duality can be formulated. We propose a scheme in which the parameter
sets are provided with a coupling function which induces a conjugacy. The decision spaces are not supposed to have any special
structure. We examine several examples. In particular, we consider some special classes of generalized convex functions. 相似文献